<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var year=prompt("请输入年份");
        var s=year%4==0&&year%100!=0;
        var t=year%400==0;
        if(s||t){
            document.write(year+"年是闰年");
        }else{
            document.write(year+"年不是闰年");
        }
    </script>
</body>
</html>